Serotonin Transporter Protein Research Articles

Serotonin Transporter (SLC6A4) and FK506-Binding Protein 5 (FKBP5) Genotype and Methylation Relationships with Response to Meditation in Veterans with PTSD.

Meditation-based interventions are novel and effective non-pharmacologic treatments for veterans with PTSD. We examined relationships between treatment response, early life trauma exposure, DNA polymorphisms, and methylation in the serotonin transporter (SLC6A4) and FK506-binding protein 5 (FKBP5) genes. DNA samples and clinical outcomes were examined in 72 veterans with PTSD who received meditation-based therapy in two separate studies of mindfulness-based stress reduction (MBSR) and Transcendental Meditation (TM). The PTSD Checklist was administered to assess symptoms at baseline and after 9weeks of meditation intervention. We examined the SLC6A4 promoter (5HTTLPR_L/S insertion/deletion + rs25531_A/G) polymorphisms according to previously defined gene expression groups, and the FKBP5 variant rs1360780 previously associated with PTSD disease risk. Methylation for CpG sites of SLC6A4 (28 sites) and FKBP5 (45 sites) genes was quantified in DNA samples collected before and after treatment. The 5HTTLPR LALA high expression genotype was associated with greater symptom improvement in participants exposed to early life trauma (p = 0.015). Separately, pre to post-treatment change of DNA methylation in a group of nine FKBP5 CpG sites was associated with greater symptom improvement (OR = 2.8, 95% CI 1.1-7.1, p = 0.027). These findings build on a wealth of existing knowledge regarding epigenetic and genetic relationships with PTSD disease risk to highlight the potential importance of SLC6A4 and FKBP5 for treatment mechanisms and as biomarkers of symptom improvement.

Tryptophan-5-hydroxylase, serotonin transporter protein and serotonergic receptors in dilated cardiomyopathy

Tryptophan-5-hydroxylase, serotonin transporter protein and serotonergic receptors in dilated cardiomyopathy

Serotonin transporter imaging agent as a probe for β-cells of pancreas

ObjectiveDiabetes mellitus (DM) is one of the major diseases in the world. Nuclear medicine imaging may be able to detect functional status of pancreatic β cells in vivo, which might elucidate the pathological mechanisms of diabetes and develop individualized treatment plans. In this study, we evaluated the ability of [125I]ADAM, a serotonin transporter (SERT) imaging agent, as a probe for detecting pancreatic β-cell mass (BCM). MethodsIn vitro cell studies were evaluated in INS-1 cells (rat islet β cell line). Biodistribution studies were performed in male normal Sprague-Dawley rats and alloxan-induced type 1 diabetes mellitus (T1DM) rats. Distribution and expression of SERT protein in pancreas of rats were also measured by immunofluorescence staining and Western blot. ResultsIn vitro cell studies showed that the concentration of [125I]ADAM associated with the INS-1 cells was increased gradually with incubation time, and the SERT specific inhibitor, escitalopram, exhibited the inhibitory effect on this interaction. Biodistribution studies also showed that the uptake of [125I]ADAM in the pancreas of normal rats was decreased in the presence of escitalopram. However, in the T1DM rat model with a significant β cells reduction, the uptake of pancreas was increased when compared with the control. Through immunofluorescence staining and Western blot, it was found that both the endocrine and exocrine cells of the normal pancreas expressed SERT protein, and the level of SERT protein in the exocrine cells was higher than islets. In the diabetic state, the expression of SERT in the exocrine cells was further increased. ConclusionsThe SERT imaging agent, [125I]ADAM, at the present form will not be suitable for imaging β cells, specifically because there were extraordinarily high non-specific signals contributing from the exocrine cells of pancreas. In addition, we noticed that the level of SERT expression was abnormally elevated in the diabetic state, which might provide an unexpected target for studying the pathological mechanisms of diabetes.

Duloxetine improves chronic orofacial pain and comorbid depressive symptoms in association with reduction of serotonin transporter protein through upregulation of ubiquitinated serotonin transporter protein.

Chronic orofacial pain (COP) is relieved by duloxetine (DLX) and frequently causes depressive symptoms. The aim of this study was to confirm effects of DLX on pain and depressive symptoms, and to associate with their effectiveness in platelet serotonin transporter (SERT) expression, which is a target molecule of DLX and plasma serotonin concentration in COP patients with depressive symptoms. We assessed for the severity of pain and depressive symptoms using the Visual Analog Scale (VAS) and 17-item Hamilton Depression Rating Scale (HDRS), respectively. Chronic orofacial pain patients were classified into 2 groups based on their HDRS before DLX-treatment: COP patients with (COP-D) and without (COP-ND) depressive symptoms. We found that the VAS and HDRS scores of both groups were significantly decreased after DLX treatment compared with those before DLX treatment. Upregulation of total SERT and downregulation of ubiquitinated SERT were observed before DLX treatment in both groups compared with healthy controls. After DLX treatment, there were no differences in total SERT of both groups and in ubiquitinated SERT of COP-D patients compared with healthy controls; whereas, ubiquitinated SERT of COP-ND patients remained downregulated. There were positive correlations between changes of serotonin concentrations and of VAS or HDRS scores in only COP-D patients. Our findings indicate that DLX improves not only pain but also comorbid depressive symptoms of COP-D patients. Duloxetine also reduces platelet SERT through upregulation of ubiquitinated SERT. As the result, decrease of plasma serotonin concentrations may be related to the efficacy of DLX in relieving pain and depression in COP patients.

Molecular Dynamics Simulation of Serotonin Transport Protein Complex with 6-Hydroxy-1-Methyl-1,2,3,4-Tetrahydro-β-Carboline Ligand from Chocolate (Theobroma cacao L.) Isolate

6-hydroxy-1-methyl1,2,3,4-tetrahydro-β-carboline (6OHMTHβC) is a chocolate derivate that has antidepressant potency. It can increase dopamine and serotonin secretion, which leads to mood improvement. This method was carried out using computational molecular docking simulations (in silico). The research design was computational-based exploratory descriptive. The results of molecular docking showed the lowest energy score and the backbone RMSD value ≤2Å. The procedure performed was 6AWP receptor docking without ligand, with native ligand (6OHMTHβC), and with reference ligand (fluvoxamine). This study also performed molecular docking simulations of 6OHMTHβC towards 6AWP to find compounds in the receptor binding pocket. This study also performed dynamics simulations and identified the molecular determinants using PyPLIF-HIPPOS and YASARA Structure software 20.1.24.10 with the Windows 10 operating system. This study succeeded in determining the stability of the dynamics simulation of the serotonin transport protein complex with the reference ligand 6OHMTHβC for 50 ns, and this result corresponds to the RMSD value and binding energy. The determination of binding energy (BE) was calculated from the BE calculation available at YASARA and Ubuntu. The binding energy value of the original ligand was -11.6590 kJ/mol, and the reference ligand was -83880 kJ/mol. The highest RMSD value of the original ligand was 1.39292Å, while the RMSD value of the reference ligand was 1.71072Å. The essential amino acid carried out was 438Ser with hydrogen bond interactions, so 6OHMTHβC was considered a competent antidepressant candidate.

Biomarkers of Affective Dysregulation Associated with In Utero Exposure to EtOH.

Children with fetal alcohol spectrum disorders (FASD) exhibit behavioral and affective dysregulation, including hyperactivity and depression. The mechanisms are not known, but they could conceivably be due to postnatal social or environmental factors. However, we postulate that, more likely, the affective dysregulation is associated with the effects of EtOH exposure on the development of fetal serotonergic (5-HT) and/or dopaminergic (DA) pathways, i.e., pathways that in postnatal life are believed to regulate mood. Many women who use alcohol (ethanol, EtOH) during pregnancy suffer from depression and take selective serotonin reuptake inhibitors (SSRIs), which might influence these monoaminergic pathways in the fetus. Alternatively, monoaminergic pathway abnormalities might reflect a direct effect of EtOH on the fetal brain. To distinguish between these possibilities, we measured their expressions in fetal brains and in fetal brain-derived exosomes (FB-Es) isolated from the mothers' blood. We hypothesized that maternal use of EtOH and/or SSRIs during pregnancy would be associated with impaired fetal neural development, detectable as abnormal levels of monoaminergic and apoptotic biomarkers in FB-Es. Fetal brain tissues and maternal blood were collected at 9-23 weeks of pregnancy. EtOH groups were compared with unexposed controls matched for gestational age (GA). The expression of 84 genes associated with the DA and 5-HT pathways was analyzed by quantitative reverse transcription polymerase chain reaction (qRT-PCR) on microarrays. FB-Es also were assayed for serotonin transporter protein (SERT) and brain-derived neurotrophic factor (BDNF) by enzyme-linked immunosorbent assay (ELISA). Six EtOH-exposed human fetal brain samples were compared to SSRI- or polydrug-exposed samples and to unexposed controls. EtOH exposure was associated with significant upregulation of DA receptor D3 and 5-HT receptor HTR2C, while HTR3A was downregulated. Monoamine oxidase A (MAOA), MAOB, the serine/threonine kinase AKT3, and caspase-3 were upregulated, while mitogen-activated protein kinase 1 (MAPK1) and AKT2 were downregulated. ETOH was associated with significant upregulation of the DA transporter gene, while SERT was downregulated. There were significant correlations between EtOH exposure and (a) caspase-3 activation, (b) reduced SERT protein levels, and (c) reduced BDNF levels. SSRI exposure independently increased caspase-3 activity and downregulated SERT and BDNF. Early exposure to EtOH and SSRI together was associated synergistically with a significant upregulation of caspase-3 and a significant downregulation of SERT and BDNF. Reduced SERT and BDNF levels were strongly correlated with a reduction in eye diameter, a somatic manifestation of FASD. Maternal use of EtOH and SSRI during pregnancy each was associated with changes in fetal brain monoamine pathways, consistent with potential mechanisms for the affective dysregulation associated with FASD.

Determination of New 4-Aryl-pyrido[1,2-c]pyrimidine Derivatives, Potential Antidepressant Agents with a High Affinity to 5-Hydroxytryptamin 1A Receptor and Serotonin Transporter Protein Receptor, with Capillary Electrophoresis

A novel capillary electrophoresis method was developed for the determination of new 4-aryl-pyrido[1,2-c]pyrimidine derivatives, potential antidepressant agents, in serum. The derivatives have conformationally restricted tryptamine moiety in pharmacophore portion and exhibit high affinity to molecular targets: 5-HT1A receptor and serotonin transporter protein. The separation process was conducted using an eCAP fused-silica capillary, detection wavelength 214 nm, 200 mM phosphate buffer adjusted to pH = 8.0, temperature 20 °C, voltage 5 kV. The proposed method was validated by determining its linearity in the concentration range of 200–1000 ng/mL. A satisfactory linearity was obtained for the method, with R2 from 0.9978 to 0.9999 for all five derivatives and a limit of quantification level from 287.1 to 310.1 ng/mL. The recoveries for all derivatives were in the range from 94.7 to 100%. The speed of obtaining the result of the analysis was only 3 min. The developed method allows to determine all five derivatives both in water solutions and serum.

Establishment of a 3D multicellular placental microtissues for investigating the effect of antidepressant vortioxetine

The placenta is a unique organ with an active metabolism and dynamically changing physiology throughout pregnancy. It is difficult to elucidate the structure of cell-cell and cell-extracellular matrix interactions of the placenta in in vivo studies due to interspecies differences and ethical constraints. In this study, human umbilical cord vein cells (HUVEC) and human placental choriocarcinoma cells (BeWo) were co-cultured for the first time to form spheroids (microtissues) on a three-dimensional (3D) Petri Dish® mold and compared with a traditional two-dimensional (2D) system. Vortioxetine is an antidepressant with a lack of literature on its use in pregnancy in established cultures, the toxicity of vortioxetine was studied to investigate the response of spheroids representing placental tissue. Spheroids were characterised by morphology and exposed to vortioxetine. Cell viability and barrier integrity were then measured. Intercellular junctions and the localisation of serotonin transporter (SERT) proteins were demonstrated by immunofluorescence (IF) staining in BeWo cells. Human chorionic gonadotropin (beta-hCG) hormone levels were also measured. In the 3D system, cell viability and hormone production were higher than in the 2D system. It was observed that the barrier structure was impaired, the structure of intracellular skeletal elements was altered and SERT expression decreased depending on vortioxetine exposure. These results demonstrate that the multicellular microtissue placenta model can be used to obtain results that more closely resemble in vivo toxicity studies of various xenobiotics than other 2D and mono-culture spheroid models in the literature. It also describes the use of 3D models for soft tissues other than the placenta.

The Effect of Serotonin Transmission on Depressive and Insomnia Symptoms in Inflammatory Bowel Diseases.

The serotonergic pathway may impact the pathogenesis and the course of inflammatory bowel diseases (IBDs). The aim of this study was to investigate the relationship between 5-HT, the serotonin transporter (SERT), and the clinical course of the disease with the occurrence of sleep and mood disorders. Participants completed sleep questionnaires and the Beck Depression Inventory (BDI). Serum 5-HT, SERT protein expression, and mRNA levels were quantified. Additionally, patients treated with anti-TNF therapy were examined before and after treatment. In this study, 77 patients with IBD and 41 healthy controls (HCs) were enrolled and 24 of them were treated with anti-TNF therapy. Patients with IBD had higher 5-HT levels and SERT protein expression than the HCs, but not mRNA SERT levels (p = 0.015, p = 0.001, p = 0.069, respectively). Similar results were obtained for patients in the active state of the disease compared to the non-active state. There was a positive relationship between insomnia severity and SERT protein expression. BDI did not correlate with serotonin or SERT. After anti-TNF therapy, only 5-HT levels were decreased. 5-HT and SERT protein are overexpressed in active IBD and may represent a candidate for novel disease activity biomarkers. The correlation between the SERT protein level and the severity of insomnia symptoms might be among the underlying biochemical factors of sleep disturbances. Anti-TNF treatment might contribute to the reduction in 5-HT levels.

Palmitoylation Regulates Human Serotonin Transporter Activity, Trafficking, and Expression and Is Modulated by Escitalopram.

In the central nervous system, serotonergic signaling modulates sleep, mood, and cognitive control. During serotonergic transmission, the synaptic concentration of serotonin is tightly controlled in a spatial and temporal manner by the serotonin transporter (SERT). Dysregulation of this process is implicated in the pathogenesis of major-depressive, obsessive-compulsive, and autism-spectrum disorders, which makes SERT a primary target for prescription therapeutics, most notably selective serotonin reuptake inhibitors (SSRIs). S-Palmitoylation, the reversible addition of a 16-carbon fatty acid to proteins, is an increasingly recognized dynamic post-translational modification responsible for modulating protein kinetics, trafficking, and localization patterns in response to physiologic/cellular stimuli. In this study, we reveal that human SERTs are a target for palmitoylation, and using the irreversible palmitoyl acyltransferase inhibitor 2-bromopalmitate (2BP), we have identified several associated functions. Using a lower dose of 2BP in shorter time frames, inhibition of palmitoylation was associated with reductions in SERT Vmax, without changes in Km or surface expression. With higher doses of 2BP for longer time intervals, inhibition of palmitoylation was consistent with the loss of cell surface and total SERT protein, suggesting palmitoylation is an important mechanism in regulating SERT trafficking and maintenance of SERT protein through biogenic or anti-degradative processes. Additionally, we have identified that treatment with the SSRI escitalopram decreases SERT palmitoylation analogous to 2BP, reducing SERT surface expression and transport capacity. Ultimately, these results reveal that palmitoylation is a major regulatory mechanism for SERT kinetics and trafficking and may be the mechanism responsible for escitalopram-induced internalization and ultimately decreased cellular SERT protein levels.

Antidepressant effects of p-coumaric acid isolated from Vaccinium bracteatum leaves extract on chronic restraint stress mouse model and antagonism of serotonin 6 receptor in vitro

BackgroundVaccinium bracteatum Thunb. leaves (VBL) are used in traditional herbal medicines to treat various biological diseases. p-coumaric acid (CA), the main active component of VBL, has neuroprotective effects against corticosterone-induced damage in vitro. However, the effects of CA on immobility induced by chronic restraint stress (CRS) in a mouse model and 5-HT receptor activity have not been investigated. Hypothesis/PurposeWe investigated the antagonistic effects of VBL, NET-D1602, and the three components of Gαs protein-coupled 5-HT receptors. Additionally, we identified the effects and mechanism of action of CA, the active component of NET-D1602, in the CRS-exposed model. MethodsFor in vitro analyses, we used 1321N1 cells stably expressing human 5-HT6 receptors and CHO-K1 expressing human 5-HT4 or 5-HT7 receptors cell lines to study the mechanism of action. For in vivo analyses, CRS-exposed mice were orally administered CA (10, 50, or 100 mg/kg) daily for 21 consecutive days. The effects of CA were analyzed by assessing behavioral changes using a forced swim test (FST), measuring levels of hypothalamic-pituitary-adrenal (HPA) axis-related hormones in ntial therapeutic effects as 5-HT6 receptor antagonists for neurodegenerative diseases and depressioserum, and acetylcholinesterase (AChE), monoamines, including 5-HT, dopamine, and norepinephrine, using enzyme-linked immunosorbent assay kits. The underlying molecular mechanisms of the serotonin transporter (SERT), monoamine oxidase A (MAO-A), and extracellular signal-regulated kinase (ERK)/protein kinase B (Akt)/mTORC1 signaling were detected using western blotting. ResultsCA was confirmed to be an active component in the antagonistic effects of NET-D1602 on 5-HT6 receptor activity through decreases in cAMP and ERK1/2 phosphorylation. Moreover, CRS-exposed mice treated with CA showed a significantly reduced immobility time in the FST. CA also significantly decreased corticosterone, corticotropin-releasing hormone (CRH), and adrenocorticotropic hormone (ACTH) levels. CA enhanced 5-HT, dopamine, and norepinephrine levels in the hippocampus (HC) and prefrontal cortex (PFC) but decreased MAO-A and SERT protein levels. Similarly, CA significantly upregulated the ERK, Ca2+/calmodulin-dependent protein kinase II (CaMKII), Akt/mTOR/p70S6K/S6 signaling pathways in both HC and the PFC. ConclusionCA contained in NET-D1602 may play the antidepressant effects against CRS-induced depression-like mechanism and the selective antagonist effect of 5-HT6 receptor.

Antibiotic-induced microbial depletion enhances murine small intestinal epithelial growth in a serotonin-dependent manner.

Regulation of small intestinal epithelial growth by endogenous and environmental factors is critical for intestinal homeostasis and recovery from insults. Depletion of the intestinal microbiome increases epithelial proliferation in small intestinal crypts, similar to the effects observed in animal models of serotonin potentiation. Based on prior evidence that the microbiome modulates serotonin activity, we hypothesized that microbial depletion-induced epithelial proliferation is dependent on host serotonin activity. A mouse model of antibiotic-induced microbial depletion (AIMD) was employed. Serotonin potentiation was achieved through either genetic knockout of the serotonin transporter (SERT) or pharmacologic SERT inhibition, and inhibition of serotonin synthesis was achieved with para-chlorophenylalanine. AIMD and serotonin potentiation increased intestinal villus height and crypt proliferation in an additive manner, but the epithelial proliferation observed after AIMD was blocked in the absence of endogenous serotonin. Using Lgr5-EGFP-reporter mice, we evaluated intestinal stem cell (ISC) quantity and proliferation. AIMD increased the number of ISCs per crypt and ISC proliferation compared to controls, and changes in ISC number and proliferation were dependent on the presence of host serotonin. Furthermore, western blotting demonstrated that AIMD reduced epithelial SERT protein expression compared to controls. In conclusion, host serotonin activity is necessary for microbial depletion-associated changes in villus height and ISC proliferation in crypts, and microbial depletion produces a functional serotonin-potentiated state through reduced SERT protein expression. These findings provide an understanding of how changes to the microbiome contribute to intestinal pathology and can be applied therapeutically.

The metabolites could not be ignored: A comparative study of the metabolite norfluoxetine with its parent fluoxetine on zebrafish (Danio rerio)

The ubiquitous pharmaceuticals in aquatic environments have attracted huge attention due to their significant risks to humans and ecosystems. However, even though the knowledge of the negative effects induced by the parent pharmaceuticals is quite extensive, little is known about their metabolites for a long time. This study provides systematical knowledge about the potential toxicity of metabolite norfluoxetine and its parent fluoxetine on zebrafish (Danio rerio) at the early life stage. The results showed that the metabolite norfluoxetine had similar acute toxicity in fish with the parent fluoxetine. For the altered fish development, there was no significant difference in most cases between the two pharmaceuticals. Compared to the control, the metabolite markedly inhibited the locomotor behavior under light-to-dark transitions, which was comparable to the parent. Norfluoxetine could easily accumulate but hardly eliminate from fish, relative to fluoxetine. In addition, the accumulated fluoxetine in zebrafish may rapidly metabolize to norfluoxetine and then be eliminated through different metabolic pathways. The functional genes related to serotonergic process (5-ht1aa, 5-ht2c, slc6a4b, and vmat), early growth (egr4), and circadian rhythm (per2) were downregulated by both the norfluoxetine and fluoxetine, indicative of the same mode-of-action of norfluoxetine with its parent in these functions. Meanwhile, the alterations caused by norfluoxetine were more pronounced than that of fluoxetine in the genes of 5-ht2c, slc6a4b, vmat, and per2. The molecular docking also confirmed that norfluoxetine could bind with serotonin transporter protein in the same as fluoxetine with a lower binding free energy. Overall, the metabolite norfluoxetine could induce similar and even more toxic effects on zebrafish with the same mode of action. The different and binding energy of the metabolite norfluoxetine and its parent fluoxetine on zebrafish may be responsible for the differentiated effects. It highlights the risks of the metabolite norfluoxetine in the aquatic environment could not be ignored.

Effect of citalopram and sertraline on the expression of miRNA- 124, 132, and 16 and their protein targets in patients with depression.

This study aimed to evaluate the effect of SSRIs on the expression of miRNAs and their protein targets. In a 100 day open-label study of citalopram (n=25) and sertraline (n=25), levels of miRNA 16, 132, and 124 and glucocorticoid receptor (GR), Brain-derived neurotrophic factor (BDNF), and serotonin transporter (SERT) protein expression were measured by QRT-PCR and western blot in healthy control (n=20), patients with depression at the baseline, and same patients after 100 days of treatment. Expression levels of GR and BDNF proteins were lower in the depressed group before treatment as compared with the healthy group (P<0.0001). The SERT level was higher among the depressed group before treatment in comparison with the healthy group (P<0.0001). The level of GR and BDNF significantly increased, and SERT expression decreased after receiving sertraline (P<0.05). When the depressed group received citalopram, only SERT and GR were altered (P<0.05). Among the microRNAs' expression investigated, mir-124 and mir-132 were higher, and mir-16 was lower among the depressed compared with the healthy group (P<0.0001). Individuals receiving citalopram only showed an increase in the expression of mir-16 while administration of sertraline led to a significant increase in the expression of mir-16 and a decrease in mir-124 and mir-132 (P<0.05). This elucidated the relationship between antidepressant treatment and the expression of different microRNA that control gene expression in various pathways involved in depressed patients. Receiving SSRI can affect the level of these proteins and their relevant microRNAs.

Triptófano-5-hidroxilasa, transportador de serotonina y receptores serotoninérgicos en miocardiopatía dilatada.

Cardiomyocytes synthesize, utilize and reuptake serotonin, which is involved in the paracrine and autocrine modulation of heart activity and in the pathophysiology of some cardiovascular diseases. To determine the expression of tryptophan-5-hydroxylase (TPH) 1 and 2, serotonin transporter protein (SERT) and serotonergic receptors in hearts with dilated cardiomyopathy (DCM) compared to controls. A comparative study was performed in six tissue blocks of the left ventricular free wall (LVWL) and inter-ventricular septum from patients who died of DCM and six who died of no cardiovascular diseases (controls). Five slices from each block were obtained to determine the expression of TPH1 and TPH2, SERT and serotonergic receptors with antibodies specific for immunofluorescence. Immunofluorescence was analyzed by Student's t-test, accepting a significance level of p < 0.05. An increase in TPH1, TPH2, 5-HT2A and 5-HT2B receptors expression were observed in dilated structures compared to controls (p < 0.05). For dilated inter-ventricular septum, the 5-HT4 receptor increased its expression (p < 0.05), and SERT in PLVI compared to controls (p < 0.05). These results suggest that the increases observed in the expression of TPH, SERT, and serotonergic receptors in hearts with DCM compared to controls could play an important role in the pathophysiology of MCD in humans.

Serotonin and dopamine transporter availability in social anxiety disorder after combined treatment with escitalopram and cognitive-behavioral therapy

Selective serotonin reuptake inhibitors (SSRIs) and internet-based cognitive behavioral therapy (ICBT) are recommended treatments of social anxiety disorder (SAD), and often combined, but their effects on monoaminergic signaling are not well understood. In this multi-tracer positron emission tomography (PET) study, 24 patients with SAD were randomized to treatment with escitalopram+ICBT or placebo+ICBT under double-blind conditions. Before and after 9 weeks of treatment, patients were examined with positron emission tomography and the radioligands [11C]DASB and [11C]PE2I, probing the serotonin (SERT) and dopamine (DAT) transporter proteins respectively. Both treatment combinations resulted in significant improvement as measured by the Liebowitz Social Anxiety Scale (LSAS). At baseline, SERT-DAT co-expression was high and, in the putamen and thalamus, co-expression showed positive associations with symptom severity. SERT-DAT co-expression was also predictive of treatment success, but predictor-outcome associations differed in direction between the treatments. After treatment, average SERT occupancy in the SSRI + ICBT group was >80%, with positive associations between symptom improvement and occupancy in the nucleus accumbens, putamen and anterior cingulate cortex. Following placebo+ICBT, SERT binding increased in the raphe nuclei. DAT binding increased in both groups in limbic and striatal areas, but relations with symptom improvement differed, being negative for SSRI + ICBT and positive for placebo + ICBT. Thus, serotonin-dopamine transporter co-expression exerts influence on symptom severity and remission rate in the treatment of social anxiety disorder. However, the monoamine transporters are modulated in dissimilar ways when cognitive-behavioral treatment is given concomitantly with either SSRI-medication or pill placebo.

New insights on the phytochemical intervention for the treatment of neuropsychiatric disorders using the leaves of Michelia champaca: an in vivo and in silico approach

Context Michelia champaca L. (Magnoliaceae) has been known since ancient times for its rich medicinal properties. Objective The ethanol extract of Michelia champaca leaves (EEMC) was evaluated on depression and anxiety using in vivo and in silico studies Materials and methods Swiss albino mice were divided into control, standard, 100 and 200 mg/kg b.w. EEMC groups and for drug administration using oral gavage. The antidepressant activity was evaluated using forced swim test (FST) and tail suspension test (TST) whereas the anxiolytic activity through elevated plus maze and light and dark tests. The in silico studies included molecular docking against human potassium channel KCSA-FAB and human serotonin transporter, and ADME/T analysis. Results Open arm duration and entries were comparable between 200 mg/kg b.w. group (184.45 ± 1.00 s and 6.25 ± 1.11, respectively) and that of diazepam treated group (180.02 s ± 0.40 and 6.10 ± 0.05, respectively). Time spent in the light cubicle was higher (46.86 ± 0.03%), similar to that of diazepam (44.33 ± 0.64%), suggesting its potent anxiolytic activity. A delayed onset of immobility and lowered immobility time was seen at both the treatment doses (FST: 93.7 ± 1.70 and 89.1 ± 0.40 s; TST: 35.05 ± 2.75 and 38.50 ± 4.10 s) and the standard drug imipramine (FST: 72.7 ± 3.72 and TST: 30.01 ± 2.99 s), indicative of its antidepressant ability. In silico studies predicted doripenem to induce anxiolytic and antidepressant activity by inhibiting human potassium channel KCSA-FAB and human serotonin transporter proteins, respectively. Conclusions EEMC is a rich source of bioactive compounds with strong antidepressant and anxiolytic properties.

Mild traumatic brain injury elicits time- and region-specific reductions in serotonin transporter protein expression and uptake capacity.

The monoamine neurotransmitter serotonin (5-HT) is important for the regulation of behavior, and aberrations in 5-HT signaling are linked to several neuropsychiatric and neurodevelopmental disorders. 5-HT signaling is dependent on and tightly regulated by the functional activity of the 5-HT transporter (SERT). Neurotrauma is known to structurally and functionally impact 5-HT neuronal tracts and 5-HT signaling; however, the extent to which various forms of neurotrauma alter homeostatic 5-HT signaling through the modulation of SERT expression and/or functional uptake capacity is currently not well characterized. We aimed to better characterize the protein expression and uptake activity of SERT following mild traumatic brain injury (mTBI). A murine model of blast-induced mTBI was utilized to characterize alterations in SERT expression and function following injury. mTBI was found to decrease (≈26%) the protein levels of SERT 3 days postinjury (DPI) in the dorsal raphe nucleus (DRN), the primary locale of 5-HT neuronal cell bodies within the central nervous system. Concomitant reductions in midbrain SERT-dependent radiolabeled 5-HT uptake were observed 3 DPI (≈24%). No alterations in SERT expression were observed 10 DPI in the DRN. Additionally, no alterations in SERT expression or function were observed in prefrontal cortex samples at any time point observed. This data reveals time- and location-dependent alterations in SERT expression and function following mTBI. These studies illustrate the critical importance of ongoing research efforts to characterize the molecular effects of various forms of neurotrauma on SERT protein expression and function, which may yield novel drug targets within 5-HT systems.

The secreted protein P75 of Lactobacillus rhamnosus GG regulates the SERT expression via EGFR and NF‐κB pathway

Aim To investigate the mechanism of Lactobacillus rhamnosus GG (LGG)-secreted protein, P75, on the regulation of the expression of serotonin transporter (SERT) through the epidermal growth factor receptor (EGFR) and nuclear factor-κB (NF-κB) pathway. Methods Caco-2 cells were stimulated with LGG supernatant (LGG-super), protein P75, AG1478, and TNF-α. A rat model of post-infectious irritable bowel syndrome (PI-IBS) was constructed and treated with phosphate-buffered saline and LGG-super for 4 weeks. The levels of SERT, p-EGFR, EGFR, p-NF-κB, NF-κB, p-IκB-α, and IκB-α were detected by quantitative real-time polymerase chain reaction, Western blot, immunofluorescence, and immunochemistry. Luciferase assay was used to verify the link between NF-κB and SERT promoter. Results LGG-super and P75 upregulated the expression levels of SERT and p-EGFR and decreased the expression levels of p-IκB-α and p-NF-κB. Dual luciferase assay result suggested that NF-κB inhibited the activity of SERT promoter. In the animal experiments, 5-HT concentration increased in the PI-IBS Model group but decreased in the Model +LGG-super group compared with the control. On the contrary, the expression of SERT protein was downregulated in the PI-IBS Model group and improved in the Model +LGG-super group. The expression of p-EGFR was reduced and p-NF-κB was enhanced in the PI-IBS Model group, whereas the expression of p-EGFR and p-NF-κB was the opposite in the Model +LGG-super group. Conclusion LGG supernatant and its secreted protein, P75, upregulate the expression of SERT by activating EGFR and inhibiting the NF-κB pathway.

Understanding of the Serotonin Transporter Mechanism‐Targeting Drug Therapy

Depression and anxiety are ranked in the top five of causes of disabilities worldwide and are the most prevalent psychiatric disorders. Serotonin is a vital hormone that commonly acts as a neurotransmitter to modulate brain activity and enable communication between nervous system cells. The serotonin transporter (SERT) is a protein located within the presynaptic membrane and is activated by 5‐hydroxytryptamine (5‐HT), a chemical messenger that releases serotonin. The SERT protein re‐uptakes 5‐HT during its release, leading to the regulation of the neurotransmitter’s concentration in the synaptic cleft. Over‐activation of SERT leads to less 5‐HT, in turn lowering serotonin concentration, resulting in a higher chance of developing depression. Common drug treatments such as citalopram and paroxetine then bind at the central site, creating an outward‐open conformation. The central site of this protein is located halfway across the membrane, wedged into a cavity made up of residues from transmembrane helices. This new structure exposes a cone‐shaped extracellular vestibular that provides an open pathway to the central site. This process does not directly inhibit the serotonin transporter, but instead allosterically opens the Thr497‐Phe335 motif and creates a new binding pathway called S2. The opened S2 allows for new chemical binding that will inhibit SERT and prevent re‐uptake. Our research attempts to explore how various antidepressants prevent the re‐uptake of 5‐HT by inhibiting this serotonin transporter.